Phoenix has become the biggest gathering point and distribution hub for people migrating to the United States from Mexico.

But unlike other large cities of the Southwest, Phoenix has little history in assimilating large numbers of Hispanics. The result has been an anti-immigrant backlash.

The U.S. Border Patrol polices Phoenix's bus station and airport -- some 175 miles from Mexico -- because the city has become an unofficial port of entry, says agent Shannon Stevens.

"The Phoenix area basically is going to be used as a major transportation hub for illegal immigration, because it's going to be the first major city they get to after crossing illegally," Stevens says.

But the city isn't just a way-station for immigrants: It has also become a place for them to settle. Census figures show the percentage of the city's Hispanic population nearly doubled between 1990 and 2000 -- from 13 percent to 25 percent. No one knows what percentage are here illegally or even from Mexico. But it is largely a population of families, helping make Arizona the fifth youngest state.

Not everyone in Phoenix is adapting so willingly to this demographic and cultural shift. Activists say the undocumented are holding down wages, costing taxpayers millions for health care and education, and contributing to crime.

Randy Pullen is among the most visible activists. He led the successful fight to pass Aizona' s Proposition 200, which bars the undocumented from receiving some public benefits. He cites a claim often heard locally -- that 80 percent of all violent crime in Phoenix can be attributed to illegal aliens. There's actually very little solid information to support such assertions about illegal immigration. But this is a debate driven by emotion rather than data.